To conserve weight and space in engine blocks, while maintaining or improving performance, it is desirable to minimize the spacing between adjacent cylinder bores. However, the closer together the cylinder bores are, the more difficult it is to provide a stable effective seal with available head gasket technology, particularly in the zones at which the cylinder bores are most closely adjacent.
One of the concerns with head gaskets where cylinder bores are closely adjacent is that the gasket body portion located between the bores is relied on to provide a seal and, where armoring is used, to mount the armor, thereby to provide an effective seal at the zone of adjacency. As the width of the gasket between the bores decreases, the gasket body becomes increasingly fragile. Thus it may break away altogether, or, if it is a typical laminated gasket body, it may delaminate and thereby become ineffective for the sealing functions for which it was designed. Further, in applications where temperatures are very high, existing close bore gasket constructions may be inadequate to provide a stable and consistent seal.